In recent years, whole blood transfusion is being replaced by blood component transfusion in which only necessary components in blood are transfused into a patient, and further plasma sampling for producing a plasma preparation is being performed. Therefore, the separation of blood into blood components is carried out in the field of blood industry. In this case, blood, which is conventionally contained in a plastic blood bag, is centrifuged and separated into different components such as red blood cells, white blood cells, and platelets by using their differences in specific gravity, so that necessary components are extracted.
As illustrated in FIG. 25, a conventional blood bag 800 used for the separation of blood into blood components includes a substantially rectangular plastic bag body 801, a port 802, and transfer tubes 811, 812, 813. The port 802 and the transfer tubes 811, 812, 813 communicate with the bag body 801. The ends of the transfer tubes 812, 813 are connected to sub-bags (not illustrated) for storing separated blood components (plasma components and white blood cell components), respectively.
The separation of blood into blood components with the use of the blood bag 800 is performed in the following manner. First, the collected blood is stored in the bag body 801 via the transfer tube 811. At this time, the port 802 and the transfer tubes 812, 813 are closed. Next, the blood in the bag body 801 is centrifuged and separated into a red blood cell layer A, a plasma layer B, and a white blood cell layer C containing platelets, as illustrated in FIG. 25. Subsequently, the transfer tube 812 is opened, and pressure is applied to the bag body 801 so that the plasma layer B is transferred via the transfer tube 812 and into a sub-bag (not illustrated) that is connected to the end of this transfer tube 812. Then, the transfer tube 813 is opened, and pressure is applied to the bag body 801 so that the white blood cell layer C is transferred via the transfer tube 813 and into another sub-bag (not illustrated) that is connected to the end of this transfer tube 813. Thus, the separation of the collected blood into each of the blood components is completed.
The proportion of white blood cell components is lower than that of the other components in blood. Therefore, in the conventional blood bag 800 as illustrated in FIG. 25, the white blood cell layer C is separated as a very thin layer between the red blood cell layer A and the plasma layer B. It is not easy for the above method to transfer all the white blood cell components to the sub-bag via the transfer tube 813 without mixing the red blood cell components into the white blood cell components or without leaving the white blood cell components in the red blood cell layer A. When the white blood cell layer C is transferred to the sub-bag by moving it in the bag body 801, the white blood cell components adhere to the inner surface of the bag body 801. This makes it difficult to collect all the white blood cell components.
A blood bag that is used for the separation of blood into blood components and can solve the above problems has been proposed (see, e.g., Patent Document 1). This blood bag will be described with reference to FIG. 26.
As illustrated in FIG. 26, the blood bag 900 used for the separation of blood into blood components includes a bag body 901 for storing blood and a transfer tube 902 for transferring the collected blood to the bag body 901. The bag body 901 includes a first bag portion 911 and a second bag portion 912 on both ends, and a third bag portion 913 provided between the first bag portion 911 and the second bag portion 912. The third bag portion 913 is narrower in width than the first bag portion 911 and the second bag portion 912. The first bag portion 911, the second bag portion 912, and the third bag portion 913 have a first port 921, a second port 922, and a third port 923, from which the contents are taken, respectively.
The separation of blood into blood components with the use of the blood bag 900 is performed in the following manner. First, blood is stored in the bag body 901 via the transfer tube 902. Next, blood in the bag body 901 is centrifuged. The blood is separated into a red blood cell layer A in the first bag portion 911, a plasma layer B in the second bag portion 912, and a white blood cell layer C in the third bag portion 913. Subsequently, both the boundary portion between the first bag portion 911 and the third bag portion 913, and the boundary portion between the third bag portion 913 and the second bag portion 912 are sealed. The sealing may be performed by, e.g., a heat sealing method or a high-frequency sealing method. Then, the bag body 901 is cut into the first, second, and third bag portions 911, 912, 913 along the sealed portions. The red blood cell layer A in the first bag portion 911, the plasma layer B in the second bag portion 912, and the white blood cell layer C in the third bag portion 913 are taken out via the first port 921, the second port 922, and the third port 923, respectively.
As described above, the blood bag 900 is configured so that the bag body 901 can be sealed for each component and separated after centrifugation. Therefore, the blood can be separated into different pure blood components without any mixing of other blood components. In particular, the rate of collection of white blood cell components can be improved.